Hiya,
I'm doing a master's thesis, and my long time boyfriend is just finishing up his phD thesis. Although we both spend long hours working, we both think that it is really important to spend time together too... after all there is life after studies. You don't want to finish up with an awesome degree but be completely alone.
I think the key is to talk to your boyfriend and lay out some "ground rules". He needs to understand that your studies are important to you, but you also need to make some time to be together.

I guess the same also goes for families too...